Barbiturate therapy reduces nitrogen excretion in acute head injury

The effect of pentobarbital on nitrogen and energy metabolism was evaluated in seven severely head-injured patients (Glasgow Coma Scale 4.7 +/- 1.7) within the first week postinjury. Measured energy expenditure (% of predicted) was significantly lower in the pentobarbital group (n = 4) versus control (n = 3) (76 +/- 23% versus 132 +/- 28%, respectively, p less than 0.01). Similarly, 24-hour urinary nitrogen excretion was lower for the barbiturate group compared to control (11.2 +/- 4.0 gm versus 19.5 +/- 3.3 gm, respectively, p less than 0.01). No statistical difference was noted for urinary 3-methylhistidine excretion between the barbiturate and control groups (43 +/- 12 mcg/day versus 47 +/- 14 mcg/day, respectively, p = N.S.). Barbiturate therapy decreases measured energy expenditure and reduces nitrogen excretion without significantly altering 3-methylhistidine excretion in head-injured patients. The metabolic effects of pentobarbital may enable the ability to achieve energy and nitrogen equilibrium during metabolic support of acutely head-injured patients.